Synoptic and satellite aspects of the southwestern u.s. summer ‘monsoon’

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

Satellite infrared imagery for three years (1980, 1981, 1982) are analysed using a colour enhancement technique to derive a cloud climatology of the southwest United States summer ‘monsoon’. Diurnally‐stratified and weekly statistics are obtained for different cloud levels and used as an index of the monsoon intensity in each year. Strong diurnal variations in cloudiness, related to surface heating, are identified for July and August, as are marked interannual differences. These regional‐scale cloud variations are found to correlate more closely with the 700mb wind direction than with the height of the 700 mb pressure surface when considered for a representative station (Winslow, Arizona). A satellite‐based definition of ‘monsoon’ best considers variations of the total cloud rather than of any individual cloud level(s). Several surface and 700 mb synoptic circulation indices are identified and related statistically to the intraseasonal cloudiness changes. The most significant association is found for the variations in latitude of the Bermuda high pressure ridge that presumably relates to changes in subsidence. However, the sign of this relationship may reverse in years when other circulation systems, notably the North Pacific anticyclone, also influence the desert Southwest. Consideration of the zonal westerly index between 45 and 65°N tends to improve the correlation between the Bermuda ridge and summer monsoon cloudiness over the region. Such cloud‐circulation studies have implications not only for climate dynamics but also for ongoing solar energy research in the American Southwest.

Original languageEnglish (US)
Pages (from-to)389-402
Number of pages14
JournalJournal of Climatology
Volume5
Issue number4
DOIs
StatePublished - Jan 1 1985

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monsoon
cloud cover
summer
infrared imagery
anticyclone
surface pressure
westerly
satellite imagery
wind direction
diurnal variation
climatology
subsidence
desert
heating
climate
index

All Science Journal Classification (ASJC) codes

  • Environmental Science(all)
  • Atmospheric Science
  • Earth and Planetary Sciences(all)

Cite this

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abstract = "Satellite infrared imagery for three years (1980, 1981, 1982) are analysed using a colour enhancement technique to derive a cloud climatology of the southwest United States summer ‘monsoon’. Diurnally‐stratified and weekly statistics are obtained for different cloud levels and used as an index of the monsoon intensity in each year. Strong diurnal variations in cloudiness, related to surface heating, are identified for July and August, as are marked interannual differences. These regional‐scale cloud variations are found to correlate more closely with the 700mb wind direction than with the height of the 700 mb pressure surface when considered for a representative station (Winslow, Arizona). A satellite‐based definition of ‘monsoon’ best considers variations of the total cloud rather than of any individual cloud level(s). Several surface and 700 mb synoptic circulation indices are identified and related statistically to the intraseasonal cloudiness changes. The most significant association is found for the variations in latitude of the Bermuda high pressure ridge that presumably relates to changes in subsidence. However, the sign of this relationship may reverse in years when other circulation systems, notably the North Pacific anticyclone, also influence the desert Southwest. Consideration of the zonal westerly index between 45 and 65°N tends to improve the correlation between the Bermuda ridge and summer monsoon cloudiness over the region. Such cloud‐circulation studies have implications not only for climate dynamics but also for ongoing solar energy research in the American Southwest.",
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Synoptic and satellite aspects of the southwestern u.s. summer ‘monsoon’. / Carleton, Andrew Mark.

In: Journal of Climatology, Vol. 5, No. 4, 01.01.1985, p. 389-402.

Research output: Contribution to journalArticle

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